Multilevel inverter is a power electronic device that has many attractive features such as high-v... more Multilevel inverter is a power electronic device that has many attractive features such as high-voltage capability and near sinusoidal output making them suitable for high-power applications. On the other hand, harmonic distortion from the modern switching mode power converters has become a serious problem in utility. Total harmonic distortion (THD) minimisation is a complex problem with multiple minima. Various THD minimisation methods have been proposed in studies that just optimise the switching angles of the multilevel inverter. In this study, both dc input sources magnitude and switching angles are optimised with particle swarm optimisation (PSO) algorithm to minimise the THD of the output staircase voltage of the multilevel inverter. The impact of the proposed minimisation method on voltage magnitude optimisation and increased number of switching angles optimisation on the staircase output voltage is analysed. The effectiveness of the proposed method is validated by simulation results of a seven-level inverter. The THD, output voltage level and number of the switching angles of the proposed method are compared with other techniques and influence of the input dc sources optimisation on the THD minimisation is shown.
In this article, a fractional-order sliding mode control (FOSMC) method is presented for a wind e... more In this article, a fractional-order sliding mode control (FOSMC) method is presented for a wind energy conversion system (WECS) with variable-speed direct-drive permanent magnet synchronous generator (PMSG) under both normal and fault conditions. Under normal operation of the system, the machine side converter (MSC) is employed to meet maximum power point tracking (MPPT) requirements of the wind turbine and the grid side converter (GSC) controls the DC-link voltage and the injected reactive. Under fault condition, to meet grid code obligations, such as low voltage ride through (LVRT), the MSC adjusts the DC-link voltage instead of the GSC. Meanwhile, the active and reactive powers are controlled by the GSC. Moreover, the suggested control method is compared to the conventional control system. The results depicted that the proposed control approach has better faster dynamic response and robustness under both balanced and unbalanced condition. In addition, improving LVRT capability an...
This study investigates the robust stability analysis of an unstable second order plus time-delay... more This study investigates the robust stability analysis of an unstable second order plus time-delay (SOPTD) plant by using Fractional-Order Proportional Integral (FOPI) controllers. We assume that there are simultaneous uncertainties in gain, time-constants, and time-delay of the plant. At first, a graphical method is provided for a robust stability analysis of the closed-loop system. Then, a robust stability checking function is introduced to facilitate the robust stability analysis. Additionally, new bounds are presented to reduce the computational burden for the robust stability analysis. Finally, two examples are provided to show the correctness of the proposed method.
Journal of international Conference on Electrical Machines and Systems, 2012
Providing variable load for testing a motor in high speed conditions is usually a difficult task.... more Providing variable load for testing a motor in high speed conditions is usually a difficult task. The eddy current brake can be used in application of load testing of motors. This paper deals with construction of a novel claw pole eddy current brake which is employed as a load for a DC counter rotating motor (CRM). These kinds of motors have two inner and outer shafts that rotate in opposite directions simultaneously, which are particularly suitable for under water propulsion systems. The prototype 45KW eddy current brake consists of two parts. One of them is installed on the inner shaft of the 60KW DC CRM and the other one is installed on its outer shaft. The simulation and experimental results with prototype brakes are also analyzed by using MATLAB/Simulink and the operational characteristic of the brake is demonstrated as a function of the motor speed and current of the magnetic poles.
2015 Australasian Universities Power Engineering Conference (AUPEC), 2015
This paper presents a direct power control (DPC) design of a grid connected doubly fed induction ... more This paper presents a direct power control (DPC) design of a grid connected doubly fed induction generator (DFIG) based wind turbine system in order to track maximum absorbable power in different wind speeds. A generalized regression neural network (GRNN) is used to estimate wind speed and thereby the maximum absorbable power is determined online as a function of wind speed. Finally the proposed DPC strategy employs a nonlinear robust sliding mode control (SMC) scheme to calculate the required rotor control voltage directly. The concept of sliding mode control is incorporated into particle swarm optimization (PSO) to determine inertial weights. The new DPC based on SMC-PSO scheme has acceptable harmonic spectra of stator current by using space vector modulation (SVM) block with constant switching frequency. Simulation results on 660-kw grid-connected DFIG are provided and show the effectiveness of the new technique, for tracking maximum power in presence machine parameters variation.
This study proposes a new frequency control of islanded and storage independent wind-powered micr... more This study proposes a new frequency control of islanded and storage independent wind-powered microgrid based on coordinated robust dynamic droop power sharing. The islanded microgrid includes wind turbine as undispatchable distributed generation (DG) and fuel cell as dispatchable DG. In the first layer of control, the reverse and direct droop controls are considered for wind turbine and fuel cell, respectively. Accordingly, the outputs of reverse droop control are active and reactive powers, which are used for wind turbine. Simultaneously, the outputs of direct droop control are frequency and voltage, which are used for the fuel cell. Since the generated power of wind turbine is not constant, so the coordinated dynamic droop coefficients for both DGs are modified as a function of available wind power. Then in the second layer, robust sliding mode control is designed for setpoints tracking of both DGs to control the frequency and voltage of islanded microgrid. The effectiveness evaluation of the proposed control scheme is performed by simulation studies on the islanded microgrid in different conditions such as single-phase fault, load step change and variety of wind speeds in MATLAB/Simulink environment. Finally, results are validated experimentally through the implementation of real-time hardware-in-the-loop system.
In this paper, the object is an estimation and torque control of a claw pole eddy current dynamom... more In this paper, the object is an estimation and torque control of a claw pole eddy current dynamometer system. The eddy current dynamometer is included DC excitation coil, poles and rotational cylinder that is coupled to the electrical motor through the shaft. Load testing of electrical motor in different operating point is provided by torque control using dynamometer. The close loop system of the eddy current dynamometer is consisted of two inner and outer control loops. In the outer control loop, the torque relation should be estimated. In this regard, first the torque estimation is presented as a function of DC excitation current and rotational speed and then, the estimated torque is compared with reference torque. In the next step, the reference current is determined according to the torque error. In the inner control loop, the switching of the DC current source is done such that its output tracks the reference current. Both designed controllers for two loops are PID controllers....
2014 International Conference and Utility Exhibition on Green Energy for Sustainable Development (ICUE), 2014
This paper proposes a new direct power control (DPC) for wind turbine system driven by permanent ... more This paper proposes a new direct power control (DPC) for wind turbine system driven by permanent synchronous generator (PMSG) in order to track maximum absorbable power in different wind speeds. The desired optimum power is determined for per wind speed by lookup table. Finally new direct power control (DPC) employs input output linearization and sliding mode nonlinear controller for robust control of active and reactive power and obtaining maximum power from wind turbine. Also constant switching frequency and required pulse for converters is achieved by using space vector modulation (SVM). Simulation results on 5.7-KW wind turbine are provided Results show that the proposed controller has low error for tracking maximum power in presence wind speed variation.
Abstract This paper presents a dynamic reverse droop power-sharing scheme to control frequency of... more Abstract This paper presents a dynamic reverse droop power-sharing scheme to control frequency of micro grids based on neural networks. Micro grid is included undispatchable distributed generation (DG) such as wind turbine and dispatchable voltage source converter DG which is considered as auxiliary generation. Power sharing control strategies of distributed generation (DG) units without communication are based on the droop concept; while for the DG units in current control mode that applied in most renewable resources such as the wind, the droop control may not be implemented directly since the output of droop control is voltage amplitude and frequency. Also, the droop coefficients are constant and determined as a function of DG unit capacity. However, the generation capacity of the wind turbine is not constant. Therefore, in the proposed scheme first, the reverse droop method is provided for the wind turbine power sharing as its outputs are active and reactive power reference. Then, the dynamic coefficients are modified as a function of generalized regression neural networks. Finally, the control strategy is presented for coordinate control of wind turbine and auxiliary generator (AG) to ensure frequency stability of micro grid. The proposed control strategy is validated through extensive simulation results using MATLAB/Simulation software.
The 5th Annual International Power Electronics, Drive Systems and Technologies Conference (PEDSTC 2014), 2014
ABSTRACT This paper proposes a new direct power control (DPC) for wind turbine system driven by p... more ABSTRACT This paper proposes a new direct power control (DPC) for wind turbine system driven by permanent synchronous generator (PMSG) in order to track maximum absorbable power in different wind speeds. The desired optimum power is determined for per wind speed by lookup table. Then new direct power control (DPC) employs second order sliding mode(SOSM) nonlinear controller for robust control of active and reactive power and obtaining maximum power from wind turbine. Also constant switching frequency and required pulse for converters is achieved by using space vector modulation (SVM). Simulation results on 5.7-kw wind turbine are provided. Results show that the proposed controller has low error for tracking maximum power in presence wind speed variation.
Multilevel inverter is a power electronic device that has many attractive features such as high-v... more Multilevel inverter is a power electronic device that has many attractive features such as high-voltage capability and near sinusoidal output making them suitable for high-power applications. On the other hand, harmonic distortion from the modern switching mode power converters has become a serious problem in utility. Total harmonic distortion (THD) minimisation is a complex problem with multiple minima. Various THD minimisation methods have been proposed in studies that just optimise the switching angles of the multilevel inverter. In this study, both dc input sources magnitude and switching angles are optimised with particle swarm optimisation (PSO) algorithm to minimise the THD of the output staircase voltage of the multilevel inverter. The impact of the proposed minimisation method on voltage magnitude optimisation and increased number of switching angles optimisation on the staircase output voltage is analysed. The effectiveness of the proposed method is validated by simulation results of a seven-level inverter. The THD, output voltage level and number of the switching angles of the proposed method are compared with other techniques and influence of the input dc sources optimisation on the THD minimisation is shown.
In this article, a fractional-order sliding mode control (FOSMC) method is presented for a wind e... more In this article, a fractional-order sliding mode control (FOSMC) method is presented for a wind energy conversion system (WECS) with variable-speed direct-drive permanent magnet synchronous generator (PMSG) under both normal and fault conditions. Under normal operation of the system, the machine side converter (MSC) is employed to meet maximum power point tracking (MPPT) requirements of the wind turbine and the grid side converter (GSC) controls the DC-link voltage and the injected reactive. Under fault condition, to meet grid code obligations, such as low voltage ride through (LVRT), the MSC adjusts the DC-link voltage instead of the GSC. Meanwhile, the active and reactive powers are controlled by the GSC. Moreover, the suggested control method is compared to the conventional control system. The results depicted that the proposed control approach has better faster dynamic response and robustness under both balanced and unbalanced condition. In addition, improving LVRT capability an...
This study investigates the robust stability analysis of an unstable second order plus time-delay... more This study investigates the robust stability analysis of an unstable second order plus time-delay (SOPTD) plant by using Fractional-Order Proportional Integral (FOPI) controllers. We assume that there are simultaneous uncertainties in gain, time-constants, and time-delay of the plant. At first, a graphical method is provided for a robust stability analysis of the closed-loop system. Then, a robust stability checking function is introduced to facilitate the robust stability analysis. Additionally, new bounds are presented to reduce the computational burden for the robust stability analysis. Finally, two examples are provided to show the correctness of the proposed method.
Journal of international Conference on Electrical Machines and Systems, 2012
Providing variable load for testing a motor in high speed conditions is usually a difficult task.... more Providing variable load for testing a motor in high speed conditions is usually a difficult task. The eddy current brake can be used in application of load testing of motors. This paper deals with construction of a novel claw pole eddy current brake which is employed as a load for a DC counter rotating motor (CRM). These kinds of motors have two inner and outer shafts that rotate in opposite directions simultaneously, which are particularly suitable for under water propulsion systems. The prototype 45KW eddy current brake consists of two parts. One of them is installed on the inner shaft of the 60KW DC CRM and the other one is installed on its outer shaft. The simulation and experimental results with prototype brakes are also analyzed by using MATLAB/Simulink and the operational characteristic of the brake is demonstrated as a function of the motor speed and current of the magnetic poles.
2015 Australasian Universities Power Engineering Conference (AUPEC), 2015
This paper presents a direct power control (DPC) design of a grid connected doubly fed induction ... more This paper presents a direct power control (DPC) design of a grid connected doubly fed induction generator (DFIG) based wind turbine system in order to track maximum absorbable power in different wind speeds. A generalized regression neural network (GRNN) is used to estimate wind speed and thereby the maximum absorbable power is determined online as a function of wind speed. Finally the proposed DPC strategy employs a nonlinear robust sliding mode control (SMC) scheme to calculate the required rotor control voltage directly. The concept of sliding mode control is incorporated into particle swarm optimization (PSO) to determine inertial weights. The new DPC based on SMC-PSO scheme has acceptable harmonic spectra of stator current by using space vector modulation (SVM) block with constant switching frequency. Simulation results on 660-kw grid-connected DFIG are provided and show the effectiveness of the new technique, for tracking maximum power in presence machine parameters variation.
This study proposes a new frequency control of islanded and storage independent wind-powered micr... more This study proposes a new frequency control of islanded and storage independent wind-powered microgrid based on coordinated robust dynamic droop power sharing. The islanded microgrid includes wind turbine as undispatchable distributed generation (DG) and fuel cell as dispatchable DG. In the first layer of control, the reverse and direct droop controls are considered for wind turbine and fuel cell, respectively. Accordingly, the outputs of reverse droop control are active and reactive powers, which are used for wind turbine. Simultaneously, the outputs of direct droop control are frequency and voltage, which are used for the fuel cell. Since the generated power of wind turbine is not constant, so the coordinated dynamic droop coefficients for both DGs are modified as a function of available wind power. Then in the second layer, robust sliding mode control is designed for setpoints tracking of both DGs to control the frequency and voltage of islanded microgrid. The effectiveness evaluation of the proposed control scheme is performed by simulation studies on the islanded microgrid in different conditions such as single-phase fault, load step change and variety of wind speeds in MATLAB/Simulink environment. Finally, results are validated experimentally through the implementation of real-time hardware-in-the-loop system.
In this paper, the object is an estimation and torque control of a claw pole eddy current dynamom... more In this paper, the object is an estimation and torque control of a claw pole eddy current dynamometer system. The eddy current dynamometer is included DC excitation coil, poles and rotational cylinder that is coupled to the electrical motor through the shaft. Load testing of electrical motor in different operating point is provided by torque control using dynamometer. The close loop system of the eddy current dynamometer is consisted of two inner and outer control loops. In the outer control loop, the torque relation should be estimated. In this regard, first the torque estimation is presented as a function of DC excitation current and rotational speed and then, the estimated torque is compared with reference torque. In the next step, the reference current is determined according to the torque error. In the inner control loop, the switching of the DC current source is done such that its output tracks the reference current. Both designed controllers for two loops are PID controllers....
2014 International Conference and Utility Exhibition on Green Energy for Sustainable Development (ICUE), 2014
This paper proposes a new direct power control (DPC) for wind turbine system driven by permanent ... more This paper proposes a new direct power control (DPC) for wind turbine system driven by permanent synchronous generator (PMSG) in order to track maximum absorbable power in different wind speeds. The desired optimum power is determined for per wind speed by lookup table. Finally new direct power control (DPC) employs input output linearization and sliding mode nonlinear controller for robust control of active and reactive power and obtaining maximum power from wind turbine. Also constant switching frequency and required pulse for converters is achieved by using space vector modulation (SVM). Simulation results on 5.7-KW wind turbine are provided Results show that the proposed controller has low error for tracking maximum power in presence wind speed variation.
Abstract This paper presents a dynamic reverse droop power-sharing scheme to control frequency of... more Abstract This paper presents a dynamic reverse droop power-sharing scheme to control frequency of micro grids based on neural networks. Micro grid is included undispatchable distributed generation (DG) such as wind turbine and dispatchable voltage source converter DG which is considered as auxiliary generation. Power sharing control strategies of distributed generation (DG) units without communication are based on the droop concept; while for the DG units in current control mode that applied in most renewable resources such as the wind, the droop control may not be implemented directly since the output of droop control is voltage amplitude and frequency. Also, the droop coefficients are constant and determined as a function of DG unit capacity. However, the generation capacity of the wind turbine is not constant. Therefore, in the proposed scheme first, the reverse droop method is provided for the wind turbine power sharing as its outputs are active and reactive power reference. Then, the dynamic coefficients are modified as a function of generalized regression neural networks. Finally, the control strategy is presented for coordinate control of wind turbine and auxiliary generator (AG) to ensure frequency stability of micro grid. The proposed control strategy is validated through extensive simulation results using MATLAB/Simulation software.
The 5th Annual International Power Electronics, Drive Systems and Technologies Conference (PEDSTC 2014), 2014
ABSTRACT This paper proposes a new direct power control (DPC) for wind turbine system driven by p... more ABSTRACT This paper proposes a new direct power control (DPC) for wind turbine system driven by permanent synchronous generator (PMSG) in order to track maximum absorbable power in different wind speeds. The desired optimum power is determined for per wind speed by lookup table. Then new direct power control (DPC) employs second order sliding mode(SOSM) nonlinear controller for robust control of active and reactive power and obtaining maximum power from wind turbine. Also constant switching frequency and required pulse for converters is achieved by using space vector modulation (SVM). Simulation results on 5.7-kw wind turbine are provided. Results show that the proposed controller has low error for tracking maximum power in presence wind speed variation.
Uploads
Papers by Sam Roozbehani